In their article, Spiegel and Mureika have presented a model of
the men's 110‑m hurdles that gives good agreement between predicted and
actual race times and velocity profiles.However, using such a model to predict the effects of wind and
altitude is slightly problematic in that these effects are small, so small
discrepancies in the model lead to inaccurate predictions.Previous experiences with models of wind
assistance suggest that a good result for a model is to predict the effects
of wind and altitude to within a factor of about 2 of the true effects
(Ward-Smith, 1985, 1999; Linthorne, 1994).Better predictive ability will require some good direct experimental
results of the effect of wind and altitude on the 110‑m hurdles to
allow fine tuning of the model.The
authors' model appears to be well reasoned, but will almost certainly require
fine tuning at a later stage to give agreement with experimental results.

The magnitude of the effect of wind and
altitude predicted by Spiegel and Mureika’s model appears to be too
great.The predicted effect of a +2.0
m.s‑1 wind on the 110‑m hurdles is 0.19 s.The effect of a +2.0 m.s‑1
wind on the 100‑m sprint is 0.10 s (Linthorne, 1994), and one would
expect a similar effect in the 110‑m hurdles, as explained below.The authors acknowledge that their results
are surprising, and this should have triggered an investigation as to why
their predictions are "out".

The hurdle clearance stride is not likely
to be a significant source of extra time from wind and altitude effects.In a 100‑m sprint the athlete usually
takes about 45 strides (= 0.45 strides per meter), and in the 110‑m
hurdles the athlete has a similar number of strides per distance (8 start
strides + 9´3 in-between strides + 10 clearance
strides + 6 run-in strides = 51 strides, which is equivalent to 0.46 strides
per meter).The authors take into
account the hurdle clearance stride where there is only the aerodynamic force
acting on the athlete, but the extra distance of the hurdle clearance stride
is only 0.5 m, and during this time the athlete reduces frontal
area.The effect of the clearance
stride is therefore expected to be negligible or to even reduce the
effect of wind on the total race time (compared to the 100‑m sprint).

In the hurdles race the athletes run at a
slower speed (9.0 m.s‑1 vs 11.5 m.s‑1),
which will reduce the effect of wind on the race time, but the athletes run
for a longer duration (13 s vs 10 s), which will increase the effect of
wind.These two effects will come
close to canceling each other, with possibly the slower speed dominating
because of the v2 form of wind assistance.Overall you would expect the predicted
effect of a +2.0 m.s‑1 wind in the 110‑m hurdles to be
almost the same as in the 100‑m sprint; about 0.10 s.

The best argument that the author's
predicted effects of wind and altitude are overestimates lies with the
calculated top-ten finishes (their Table 4).The list has a strong bias towards negative wind readings, when you
would expect a random distribution of wind readings.The order of wind readings in Table 4 is ‑1.6,
‑0.1, ‑0.2, ‑0.5, 0.0, 0.2, 0.5, 0.6, 0.9, 1.6, and
1.5.Also, you would expect one or two
performances from the non-legal list (Table 3) to make the top-ten finishes
list, but none do, and most come nowhere near making the list.The results presented in Table 4 should
have sent the alarm bells ringing and triggered a re-examination of the
model, the assumptions of the model, and the parameter values used in the
simulations.

In the first version of the manuscript,
the authors did not adequately reference the work of Ward-Smith.He developed a mathematical model of the
effect of the wind on 100‑m sprint times (Ward-Smith, 1985), and he
extended this model to calculate the effect of wind on the 110‑m
hurdles (Ward-Smith, 1997).The model
includes the energy required to raise the center of mass up over the hurdle
(about 30 cm).This aspect of the
event was not included in Spiegel and Mureika’s model.Ward-Smith predicted that a +2.0 m.s‑1
wind reduces a 110‑m hurdle race time by 0.24 s.However, this result was obtained using an
old version of his wind effects model.He recently revised his 100‑m wind effects model (Ward-Smith,
1999) to bring the predicted effect of a +2.0 m.s‑1 wind
into line with the experimental results of Linthorne (1994).Applying a similar correction (0.18 s with
the old 100‑m model; 0.10 s with the revised 100‑m model) to his
110‑m hurdles result gives a revised prediction of 0.13 s.This revised prediction is likely to be
closer to the true wind effects value than the 0.19 s predicted by Spiegel
and Mureika.

References

Ward-Smith AJ (1985).A
mathematical analysis of the influence of adverse and favourable winds on
sprinting. Journal of Biomechanics 18, 351-357